Agricultural sprayers are used by farmers and contractors to apply pesticides and other nutrient-containing solutions to crop fields. Sprayers can be mounted to, or towed by, a tractor or other suitable vehicle or may be self-propelled with an integrated means of propulsion and a drivers cab. The sprayer machine typically includes a storage tank for the liquid to be applied, the tank being filled as required by the operator.
The liquid is applied to the field by a number of liquid application devices, typically spray nozzles, which are mounted in a spaced relationship along the length of a boom which, itself, is mounted to the sprayer vehicle. The nozzles are each connected to the storage tank by liquid delivery means comprising various pipes, valves, pumps and other plumbing. The liquid is atomised by the nozzles and applied to the crop in a jet of mist for example.
The length of the boom determines the operating width of the sprayer. Driven by economies of scale, there is a growing demand for sprayer manufacturers to produce machines with longer spray booms. However, increasing the boom length significantly increases the risk of structural failure due to the increased stress placed upon the hinges and joints caused by natural vibrations and oscillations which pass from the spray vehicle along the boom. Today, boom lengths of conventional truss-style construction are approaching theft physical limits with any further increase in length requiring significant strengthening of the joints, mountings and hinges between sections and along the boom.
Booms having a truss-style construction suffer from peak stresses at the nodes where diagonal brace members are secured to the upper and lower beams. Conventionally welded joints have been employed to secure the braces but these dictate the structural strength of the overall boom and are known to crack or fail completely under high load conditions.